But you're making an argument that's been so easily and laughably debunked that I just gotta pile on.
Imagine trans-ness is left-handedness. For centuries, left-handed kids were abused into the Right Way (no pun intended, and also an oddly astute observation on today). After the stigma of left-handedness was rather quickly done away with, we saw an absolutely meteoric rise in the number of kids identifying as Leftie...until it plateaued, at a representative level. Turns out that when you suddenly free a group to exist, they have a period of massive growth as they become free to be recognized, and then they settle down into a normal, accepted, if small part of society.
Kids aren't all suddenly being "brainwashed" into being trans, rather the kids who are actually trans are feeling safe to come out now. Your dreaded "unreal rise" is not only very real and accountable for, it'll stabilize at (i'd guess) 1.5-2%. That's how people under 18 identify, and despite people like you I'm postulating America has become safe enough that most trans kids will come out now.